A ship under operation receives ballast water from the outside to keep the ship balanced. In this way, the ballast water introduced into the ship is sterilized and stored in the ship, and when discharging outside, the ballast water is discharged to the outside after being neutralized by introducing a neutralizing agent to the ballast water.
The ballast water introduced into the ship is filtered by using one of mechanical, physical, or chemical method to remove solids and microorganisms contained in the ballast water. In this case, as for the mechanical method, a filtering method can be used for the ballast water which should be sterilized of microorganisms.
As for the filter for the ballast water, the filter can be an edged wire, a wire mesh, or a disk typed filter.
And, as for the physical method, an UV (ultraviolet rays) irradiating method and an AOP (advanced oxidation process) method for generating OH radicals can be used for the ballast water which should be sterilized of microorganisms.
Besides, as for the chemical method, using the chlorine-based fungicides or electrolysis, a hypochlorite (HClO) and hypochlorite ion (OCl—) producing method can be used to treat the ballast water which should be sterilized of microorganisms.
As for another example of the chemical method, it is possible to use a method of adding chemicals such as O3, ClO3.
However, among the sterilization methods of ballast water using the methods described above, the mechanical method has disadvantages in that it is difficult to wash out the scum attached to a filter, whereby, in case of using a screen filter such as edged wire or a mesh typed wire filter, clogging can be occurred due to solid.
And, the physical method has disadvantages in possibility of regrowth of microorganisms due to the absence of remaining sterilizing microorganisms. Also, the chemical method has disadvantages in that an additional process is needed to neutralize residual chemicals in the ballast water. These methods have a drawback that there is a limit for sterilizing microorganisms.